Hi Tim,

<If I create a solid inside another but with a surface level with another , I find the smaller one hard to select, how should I do this?>

I often work with two versions of MoI open at the same time, one for the job I'm designing in & one for "Copy & Paste" of various parts.
I can then use the "parts version" to store various pieces in their correct position, while I continue to work in the "design version".
It's also handy for those designs where you get a "second idea" while working on the first one or when you've got a lot of parts to "Boolean Difference".
In the "design version", I can then Hide or Delete those various parts knowing that I can just Copy & Paste back from the "parts version".

Hope this makes sense, Colin